Take out the cartridge and see if it looks really dirty. If it looks fine, then there isn't really any reason why you couldn't keep using that one for an extra week or two.
When I change cartridges out of one of my tanks, I do a partial water change as well. I get a small bucket and take some water out of the tank and then rinse/shake off the cartridge in that water (to try and throw off any bacteria into the water so the new cartridge and pick some up). Then I take the new cartridge and rinse it off (or you can soak it for a little bit, like half an hour after shaking it around) in the dirty tank water.
In my experience, this helps to seed the new cartridge, even if just a little, so my tank's water parameters don't get all messed up.

The packaging on my cartridges says to rinse it off for about 10 seconds under running water to activate the carbon and to remove dust, but you don't need to worry about doing that since the water from the sink has chlorine in it (which can kill the bacteria when you try rinsing it around in the bucket of dirty water/water with all that bacteria). I've always just thrown the new cartridge straight into the bucket without rinsing and never had any issues.

I would leave the cartridge alone for AT least a month. You haven't even put the fish in there.

If you mess with the media now, you risk messing up the cycle if it really has completed.

My tank cycled 07-21 & I haven't done ANYTHING since then other than a 50% siphoning and rearrangement of the tank.

I'm going to have to clean the other half of the tank because of all of the live foods I've been feeding them over the past 2 days.

Currently water results for me are 0.0 ppm nitrite & .50 ppm ammonia

I was going to ask you what kind of tank, filter, etc...

Nevermind...

Here's your info & the date you posted it.

What are your current water results?

07-08-2012, 08:43 PM

Info:
~ 5 gallon aquarium; Aqueon Mini Bow
~ built in filter ^
~ light hood; not on for cycling purposes
~ heater made for 2.5-5 gal tanks; constant 8.0 (°F)
~ got rid of Tetra Whisper Air Pump because it was too strong
~ no airstone, for obvious reasons ^
~ over an inch thick of gravel & purple acrylic jewels
~ baby java ferns strewn around the bottom of the aquarium
~ decor, such as pots and such
~ no beneficial bacteria available to seed

I would leave the cartridge alone for AT least a month. You haven't even put the fish in there.

If you mess with the media now, you risk messing up the cycle if it really has completed.

My tank cycled [2012-07-21] & I haven't done ANYTHING since then other than a 50% siphoning and rearrangement of the tank.

I was going to ask you what kind of tank, filter, etc...

Nevermind...

Here's your info & the date you posted it.

What are your current water results?

07-08-2012, 08:43 PM

Info:
~ 5 gallon aquarium; Aqueon Mini Bow
~ built in filter ^
~ light hood; not on for cycling purposes
~ heater made for 2.5-5 gal tanks; constant 8.0 (°F)
~ got rid of Tetra Whisper Air Pump because it was too strong
~ no airstone, for obvious reasons ^
~ over an inch thick of gravel & purple acrylic jewels
~ baby java ferns strewn around the bottom of the aquarium
~ decor, such as pots and such
~ no beneficial bacteria available to seed

Also, MSG: I do not have the air pump & aerator anymore. It was too strong for Bubba & the tank.

Otherwise, everything else is the same! Besides the 1 Amano shrimp hiding somewhere (probably still grieving the loss of his other shrimp friend).

I am not going to replace the cartridge JUST YET, but do you guys know how I can stick a NEW carbon filter cartridge in there w/o losing all of the BB in the current one cycling the tank?

Also, Bubba has been in the tank for a whole week + some days now. I have fishless cycled the tank for 3 weeks... up until vacation came & had no choice but to add him & the shrimp in 2 days prior to leaving.